Apparatus and method for degassing a liquid

ABSTRACT

Apparatus and method for removing entrapped gases from liquids by, simultaneously, mechanically agitating the liquid to be processed and drawing a partial vacuum over the free surface of such liquid.

United States Patent INTAKE Nold [45] July 18, 1972 54 PPARATUS AND METHOD FOR 2,376,221 5 1945 Baker ..55/52 x 2,350,534 6/1944 Rosinger..... 259/D1G. 46 DEGASSING A LIQUID 3,160,138 12/1964 Platzman ..55/52 X [72] Inventor: Walter E. Nold, 24 Birch Road, Natick, 2,180,051 11/1939 Hickman ..55/52 X Mass. 01760 2,518,758 8/1950 Cook 259/DIG. 46 2,784,150 3/1957 Rose et a1. 259/D1G 46 [22] filed 1971 3,211,433 10/1965 Chrostowski m1. ...259/D1G 46 21 App| N 112, 9 3,529,405 9/1970 Ashbrook ..55/277 X Related US. Application Data Primary Examiner-Reuben Friedman Assistant ExaminerR. W. Burks lCgygnuation-m-part of Ser. No. 59,110, -July 29, A"0mey Phi1ip McFarland [57] ABSTRACT [52] US. Cl ..55/192, 23/259 [51] lnt.Cl ..B0ld 19/00 3 App r and meth d for removing entrapped gases from [58] 'Field of Search ..23/253, 259; 55/15, 36, 52, liquids y simultaneously, mechanically agitating the liquid to 55 55 5 199 203; 259mm. 4 be processed and drawing a partial vacuum over the free surface of such liquid. [56] References Cited UNITED STATES PATENTS 2 Claim, 4 Drawing Figures 2,908,652 10/1959 Forrester ..55/52 OUTLE PATENTEDJIMBMTZ 3.676583 SHEET 10F 2 VACUUM PUMP [/8 VACUUM 22, PUMP Ma /6 /a l6 r g VACUUM DRIVER f" PUMP mq h .'/VVEN7'0/? WALTER E, NOLD PMENn-tumwmz 3.676383 SHEEI 2 or 2 INTAKE OUTLET M/VE/VTOR WALTER E. IVOLD APPARATUS AND METHOD FOR DEGASSING A LIQUID CROSS-REFERENCES TO RELATED APPLICATIONS This is a continuation-in-part of application Ser. No. 59,1 l0,filed July 29, 1970.

BACKGROUND OF THE INVENTION This invention pertains generally to purifying apparatus and method and particularly to apparatus and method for degassing liquids.

It is known in the art that air, or other kinds of gases, may be removed from liquids, such as water, whenever the concentration of a gas in a liquid must be reduced. For example, in the testing of hermetic seals it is common practice to immerse a sealed device in water and then to observe whether or not air bubbles originate at the seal. In such an application it is, of course, highly desirable that any air in the liquid be removed before testing begins in order to avoid masking of the effect being observed. I

The removal of most of the entrapped gases from a liquid is ordinarily accomplished by placing the liquid in a vacuum flask and then, simultaneously, heating the liquid and drawing a vacuum. In practice such a process permits the concentration of entrapped gases to be reduced to the order of three to four parts per million without too much difficulty. While such a concentration is sufficiently low for many applications, it is sometimes necessary to reduce the concentration even more.

. To accomplish such an end with known processes it is necessary to recycle and to use a hard vacuum. Even when 3 to 4 parts per million of entrapped gas is tolerable, the fact that the liquid is heated normally causes difficulty, it being evident that the de-aerated liquid must usually be cooled before use. Such a requirement obviously makes it necessary to provide a heat exchanger of some type or other in the system.

It is a primary object of this invention to provide improved apparatus and method for removing entrapped gases from a liquid.

Another object of this invention is to provide apparatus and method for removing entrapped gases from a liquid which operate without any requirement of heating the liquid.

SUMMARY OF THE INVENTION AND DESCRIPTION OF THE DRAWING These and other objects of this invention are attained generally by placing the liquidto be processed in a vacuum flask and then, while drawing a vacuum, violently agitating the liquid. For a more complete understanding of this invention, reference is now made to the detailed description of the accompanying drawings in which:

FIG. 1 is side view of a preferred embodiment of this invention illustrating the contemplated principle of agitating and drawing a vacuum to de-aerate a liquid;

FIG. 2 is an alternative embodiment of this invention;

FIG. 3 is still another alternative embodiment of this invention; and

FIG. 4 is a cross-sectional view of another embodiment of this invention, such view showing a quantity of partially processed liquid.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, it may be seen that a liquid (not numbered) to be processed is placed in a vacuum flask along with a number of magnetizable rods 12. A stopper 14, through which a tube 16 passes as indicated, closes the mouth of the vacuum flask 10. The tube 16 in turn is connected to a vacuum pump 18. Adjacent to the bottom of the vacuum flask 10 is a C-shaped permanent magnet 20 which in turn is mounted in any convenient manner on the rotor shaft 22 of a motor 24.

It may be seen that when the motor 24 is energized, the C- shaped permanent magnet 20 is caused to rotate and that the magnetic field therefrom couples through the bottom of the vacuum flask 10 to the magnetizable rods 12. The latter then are caused to rotate, thereby causing the liquid within the vacuum flask to be agitated. The speed of the motor 24 may be varied within wide limits; I have found, however, that a speed between 1,200 and 1,800 rpm gives good results. In any event, as the liquid is agitated, gases entrapped in the liquid are freed and are removed by the vacuum pump 18 through the tube 16. The vacuum pump 18 may be of any conventional construction; I have found even that satisfactory results may be attained by using tube 16 as a Venturi tube to provide suction. With such an arrangement I have found that the 60116611 tration of gases in water may be reduced to approximately 1.2

parts per million.

Referring now to FIG. 2, wherein elements common to elements in FIG. 1 are correspondingly numbered, it may be seen that the alternative embodiment illustrated in FIG. 2 differs from the preferred embodiment by reason of the way in which the liquid is agitated. Thus, in the embodiment shown in FIG. 2, the rotor shaft 22 of the motor 24 is passed through the stopper 14a and is connected to vanes 26. Therefore, when the motor 24 is energized the vanes 26 are caused to rotate to agitate the liquid. It is noted here in passing that special care need not be taken to provide a perfect air seal between the rotor shaft 22 and the stopper 14a because any air which may leak through such bearing is removed by operation of the vacuum pump 18.

Referring now to FIG. 3, wherein elements common to FIGS. 1 and 2 are correspondingly numbered, it may be seen that the manner in which agitation of the liquid is accomplished may be varied in still another way. Thus, in FIG. 3 an ultrasonic transducer 28, as a piezo-electric crystal, is suspended in any convenient manner (not shown) in the liquid within the vacuum flask 10. A driver 30 for the ultrasonic transducer 28 is connected, through the stopper 140, by wires 32 to the such transducer. Thus, when the driver 30 is energized, the ultrasonic transducer 28 is caused to vibrate to effect agitation of the liquid.

Referring now to FIG. 4, still another embodiment of my invention, wherein agitation of the liquid to be degassed is accomplished through utilization of the phenomenom of cavitation, is shown. Thus, in FIG. 4, a sealed tank 41 is provided, such tank corresponding to the sealed flask of the embodiments described hereinbefore. The bottom (not numbered) of the sealed tank 41 is, preferably, formed as shown, to provide a bearing (not numbered) for the driven part of a magnetic clutch 43 (to which is affixed, in any convenient manner, an impeller 45 which has a number of vanes (not numbered). The driving part of the magnetic clutch 43 is attached to a shaft 47 of an electric motor 49. It is evident, therefore, that whenever the electric motor 49 is energized from a power source (not shown), the magnetic clutch 43 is operative to rotate the im' peller 45 without requiring a vacuum seal for a rotating member passing through the bottom of the sealed tank 41. Liquid to be degassed is admitted to the sealed tank 41 through a pipe 51 from a source (not shown) whenever an intake valve 53 is opened. It should be noted here that it is much preferred, although not essential to my invention, to shape the pipe 51 within the sealed tank 41 to direct the liquid to be degassed against the impeller 45. Spacer rods, as rods 55, 550, (one of which is hollow and extends through the bottom of the sealed tank 45 to provide a way of drawing a vacuum within the sealed tank 41 by a vacuum pump, not shown) are disposed in any convenient manner inside the sealed tank 45 to support a pair of vortex spoilers 57, 59. The latter simply are plates, the former being solid and supported in proximity to the upper surface of the impeller 45 and the latter having an opening (not numbered) formed therethrough. The position of the vortex spoilers S7, 59 within the sealed tank 41 is not critical. To complete the embodiment shown in FIG. 4, a pipe 61 and outlet valve 63 are disposed as indicated to permit degassed liquid to be withdrawn from the sealed tank as desired.

In operation, a partial vacuum (say a vacuum of 28 to 29.5 inches of mercury) is drawn in the sealed tank 41 before any liquid to be degassed is introduced thereto. The electric motor 49 is energized to cause the impeller 45 to be rotated as described hereinbefore. If the pipe 51 is bent so as to direct the liquid to be degassed on to the impeller, such liquid initially is broken into droplets, thereby increasing the surface area of such liquid to the partial vacuum. Such an increase, in turn, permits any gases entrapped in the liquid to be removed rapidly. As the level of the liquid within the sealed tank 41 rises above the level of the impeller 45, cavitation in the liquid starts. As that phenomenom builds up, the space immediately surrounding the vanes of the impeller 45 cannot be filled with the liquid to be degassed. Rather, a partial vacuum exists in such space and liquid to be degassed thereafter introduced is violently agitated and broken into a mist-like spray. The surface area of the droplets in such a spray is, obviously, very much greater than the surface area of the liquid out of the pipe 51 so the entrapped gases in the spray are quickly moved into the partial vacuum in the space in which cavitation occurs. Such air then leaks around the vortex spoiler 57 as a train of bubbles, passing upwardly through the liquid in the sealed tank 41 to collect under the vortex spoiler 59. The gas under the latter spoiler then rises through the opening therein, through the surface of the liquid to the partially evacuated space above such surface. The so released gas is then withdrawn from the sealed tank 41 through spacer rod 55. With a sealed tank having a capacity of 1 gallon, gases entrapped, i.e. dissolved, in water may be removed at a rate of 4 gallons per hour. That is, the concentration of gases dissolved in water may be reduced from about to 0.2 parts per million.

It will be recognized that, in the absence of the vortex spoilers 57, 59, the motion of the impeller 45 would cause a vortex to be formed in the liquid in the same manner as in the embodiments previously discussed. Such a vortex obviously does not serve any useful purpose in the present case but rather, if anything, reduces the amount of liquid which may be processed in a sealed tank of a given size.

it should be noted here that the phenomenom of cavitation in a liquid may be induced by sound waves as well as by a moving impeller as shown in FIG. 4. Therefore, it will be obvious that the embodiment. of my invention shown in FIG. 3 may, with a proper ultrasonic transducer, be operated in essentially the same manner as the embodiment shown in FIG. 4 to take advantage of cavitation.

While I have chosen to illustrate my invention by means of several simple alternate embodiments of apparatus, it is felt that such embodiments also illustrate my contemplated method, which is: (l) placing a liquid to be degassed in a vacuum chamber; and (2) simultaneously mechanically agitating the liquid and drawing a partial vacuum on the exposed surface of the liquid. Further, it is felt that the many changes may be made in the illustrated apparatus without departing from my inventive concepts. For example, it is evident that liquid intake and outlet piping and valves may be provided to permit at least a sembcontinuous process to be carried on. Further, it is evident that the principles of the illustrated invention would be applicable to degassing any liquid. It is felt, therefore, that this invention should not be restricted to its illustrated embodiments, but rather should be limited only by the spirit and scope of the appended claims.

What is claimed is:

1. Apparatus for removing gases from a liquid comprising:

a. a vacuum flask for holding the liquid to be processed;

b. means for introducing such liquid within the vacuum flask;

c. a vacuum pump having its intake connected to the vacuum flask for removing gases freed from such liquid; (1. means for agitating such liquid to induce cavitation therein including at least one vane rotatably mounted within the vacuum flask and immersed in such liquid; e. means for rotating the at least one vane to induce cavitation in such liquid;

f. means, including at least one disposed within such liquid,

for inhibiting the formation of a vortex in such liquid.

2. Apparatus as in claim 1 wherein the means for introducing liquid to be processed within the vacuum flask includes a pipe passing through a wall of such flask, the end of such pipe within such flask being disposed adjacent to the means for agitating such liquid as it is introduced into such flask. 

1. Apparatus for removing gases from a liquid comprising: a. a vacuum flask for holding the liquid to be processed; b. means for introducing such liquid within the vacuum flask; c. a vacuum pump having its intake connected to the vacuum flask for removing gases freed from such liquid; d. means for agitating such liquid to induce cavitation therein including at least one vane rotatably mounted within the vacuum flask and immersed in such liquid; e. means for rotating the at least one vane to induce cavitation in such liquid; f. means, including at least one disposed within such liquid, for inhibiting the formation of a vortex in such liquid.
 2. Apparatus as in claim 1 wherein the means for introducing liquid to be processed within the vacuum flask includes a pipe passing through a wall of such flask, the end of such pipe within such flask being disposed adjacent to the means for agitating such liquid as it is introduced into such flask. 